JPH05229277A - Printing offset blanket - Google Patents

Abstract

PURPOSE:To prevent the transfer of a water repelling component to the surface of an object to be printed composed of a surface printing layer by laminating the surface printing layer composed of specific silicone rubber on a support layer to form a printing offset blanket. CONSTITUTION:A printing offset blanket is produced by laminating a surface printing layer composed of silicone rubber wherein the concns. of low mol.wt. siloxane with a polymerization degree of 20 or less and non-functional silicone oil on the surface of the printing layer are respectively 1500ppm on a support layer. Even when the surface printing layer of this offset blanket is brought into contact with the surface of glass, the surface water or ink repellency of glass is not almost confirmed and good three primary colors printing can be performed. As the aforementioned silicone rubber, there are methyl vinyl silicone rubber, fluorosilicone rubber having a trifluoropropyl group and phenylsilicone rubber having a phenyl group.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing offset blanket used for lithographic offset printing or gravure offset printing, and more particularly to a printing offset blanket suitable for printing fine patterns such as liquid crystal color filters. It is a thing.

[0002]

2. Description of the Related Art When an ink layer printed on a transparent glass surface such as a liquid crystal color filter consisting of three colors of red, green and blue is viewed by transmitted light, the ink layer film is formed. If there is a variation in thickness, the transmitted light will have light and shade, which causes variations in image quality. In order to prevent such variations in film thickness, the ink on the plate is transferred to the glass surface through the offset blanket during the three-color printing of red, green, and blue on the glass surface by lithographic offset printing or gravure printing. It needs to be completely transcribed. However, usually, in a conventional offset blanket using a rubber material such as acrylonitrile-butadiene copolymer rubber (NBR) as a surface printing layer, the ink remains on the surface of the blanket and separates on the glass and the blanket, and thus the ink layer Unevenness inevitably occurs on the surface of
The film thickness varies.

Therefore, the inventors of the present invention have tested various rubber materials, and when silicone rubber is used as a surface printing layer of an offset blanket, the ink on the blanket can be almost completely transferred onto the glass, which is extremely high. We have found that a flat ink layer can be obtained. However, in the above three-color printing, it is necessary to print three times in order to sequentially form the patterns of the ink layers of the respective colors. Therefore, when printing using an offset blanket that uses silicone rubber as the surface printing layer,
At the time of the first printing, the silicone rubber on the surface adheres to the glass surface at the non-printed portion, the water-repellent component (such as siloxane) transfers from the silicone rubber to the glass, and the second and third times at that portion. During printing, the ink was repelled on the glass, and there was a problem that printing could not be performed properly.

Further, after printing three colors, when the ITO film (transparent electrode film) is vapor-deposited on the pattern of each color, the pattern is exposed to a high temperature of about 200 ° C., so that the pattern is heat-resistant to protect it from heat. A protective film (for example, Optomer SS manufactured by Nippon Synthetic Rubber Co., Ltd.) is coated with a spin coater or the like. At this time, if the surface of the printed pattern is water-repellent, a uniform film cannot be coated, which causes pinholes. Therefore, since the surface of the print pattern also contacts the rubber on the blanket surface during printing, it is necessary to reduce the water-repellent substance on the rubber surface as much as possible.

The main object of the present invention is particularly suitable for multicolor printing of a fine pattern such as a liquid crystal color filter, in which the water-repellent component is transferred from the surface printing layer to the surface of the material to be printed,
An object of the present invention is to provide an offset blanket for printing in which ink is prevented from being repelled on the surface of a printing medium. Another object of the present invention is, in the above-described multicolor printing, the water-repellent component is transferred by the contact of the surface printing layer with the printed pattern surface, and pinholes are formed in the protective film coating the pattern surface. An object of the present invention is to provide an offset blanket for printing that prevents the occurrence of such problems.

[0006]

The rubber material of the surface printing layer of the offset blanket in the present invention comprises:
From the viewpoint of ink transfer property, it is limited to silicone rubber, but normal silicone rubber is the base silicone raw rubber (in the case of millable type silicone, the degree of polymerization is 5,000 to 10).
000 polydimethylsiloxane, and in the case of RTV silicone, polydimethylsiloxane having a polymerization degree of 100 to 800) contains a cyclic low molecular weight siloxane (polymerization degree of 3 to 20). It is well known that bleeding occurs on the rubber surface. The bleeding low-molecular-weight siloxane is extremely water-repellent and electrically insulating, and often causes contact failure in rubber parts such as touch panels.

Therefore, even when the silicone rubber is used as the surface printing layer of the offset blanket, the red ink is printed when the red ink is printed the first time and the green or blue ink is printed the second time. At that time, a water-repellent substance such as low-molecular-weight siloxane is transferred to the non-printed portion (portion where the green or blue ink is to be printed), causing a problem of repelling the green or blue ink. Also, when coating the heat-resistant protective film for depositing the ITO film (transparent electrode film) on the printed pattern of each color, if the surface of the pattern is water repellent, coat a uniform film. Because it can not be done and it causes pinholes,
It is necessary to reduce the water-repellent substance on the rubber surface as much as possible.

Usually, a method for removing the low molecular weight siloxane component is usually 2 to 5 at a temperature of about 180 to 220 ° C.
A method of scattering by secondary vulcanization that is heated for a time is generally performed. Further, among commercially available silicone rubbers, so-called low molecular weight siloxane-removing grade silicone rubbers in which low molecular weight components are forcibly sucked to remove most of them at the stage of raw rubber are also provided. Therefore, printing tests were conducted on various secondary vulcanization conditions and various low molecular weight siloxane-removing grade silicone rubbers, and the water repellency of the glass surface was evaluated (see Comparative Examples described later). As a result, the amount of low-molecular-weight siloxane decreased when the secondary vulcanization condition, that is, the vulcanization time at 200 ° C. was changed, but when judged from the aspect of the contact angle on the glass surface, the result was not so improved. It wasn't.
A similar test was conducted on a silicone rubber having a low molecular weight siloxane removal grade, but the contact angle was slightly reduced, but it was not sufficient. Therefore, it is considered that the low-molecular weight siloxane is not the only water-repellent substance that contaminates the glass surface.

Therefore, the inventors of the present invention analyzed the contaminants on the glass surface and found that, in addition to the low-molecular weight siloxane component, a considerable amount of silicone oil having no functional group and a slightly large molecular weight was contained. I found it. Based on this finding, in addition to the removal of low-molecular weight siloxane, a prototype of a silicone rubber in which a non-functional silicone oil component having no functional group was removed as much as possible was prototyped, and an offset blanket was produced using this prototype silicone rubber. As a result of a test, water repellency on the glass surface was not recognized, and three-color printing could be performed very favorably (see Examples below). Then, a quantitative analysis of the low molecular weight siloxane component and the non-functional silicone oil component of the surface of the silicone rubber that constitutes the surface printing layer of the blanket was performed, and the concentration limit that did not contaminate the glass surface that is the object to be printed was examined, It was found that the glass surface becomes water-repellent when the concentration of each of these exceeds 1500 ppm.

Therefore, the offset blanket for printing of the present invention comprises a support layer, and a surface printing layer made of silicone rubber laminated on the support layer. The surface printing layer has a low molecular weight of 20 or less and a degree of polymerization of 20 or less. The concentration of each of siloxane and nonfunctional silicone oil is 1500 ppm or less. Even if the surface printing layer of the offset blanket produced by using the silicone rubber reduced in the low molecular weight siloxane and the non-functional silicone oil is brought into contact with the glass surface, the water repellency and the ink repellency of the glass surface are almost eliminated. It is not recognized, and the three primary color printing can be satisfactorily performed.

Examples of the silicone rubber include one or a mixture of two or more selected from the group consisting of methylvinyl silicone rubber, trifluoropropyl group-containing fluorosilicone rubber and phenyl group-containing phenylsilicone rubber. However, it is not limited to these. Examples of the low molecular weight siloxane include cyclic siloxanes having a degree of polymerization of 20 or less and represented by the following formula.

[(CH ₃ ) ₂ SiO] _n (where n is the degree of polymerization) Cyclic siloxanes having a degree of polymerization exceeding 20 are excluded.
A cyclic siloxane having a degree of polymerization of 20 or more has a large molecular weight, so even if it is present in a rubber, it rarely bleeds to the surface. Even if it bleeds to the surface, it affects water repellency. Because there are few. As a method of removing the low molecular weight siloxane from the silicone rubber, for example, in addition to forcibly removing the low molecular weight siloxane by the vacuum method at the manufacturing stage, secondary vulcanization as described above may be mentioned.

The non-functional silicone oil which may be contained in the silicone rubber includes, for example, dimethyl silicone oil, methylphenyl silicone oil, methylhydrogen silicone oil and the like. Examples of the method of removing these silicone oils from the silicone rubber include a method of swelling the rubber with a solvent such as n-hexane and extracting the oil component with hexane.

As the silicone rubber used in the present invention, conventionally known various forms of silicone rubber can be used. For example, millable millable silicone rubber, room temperature vulcanizing type silicone rubber (RT) which cures at room temperature (RT).
V rubber), injection-moldable LIM (Liquid Injection M)
olding) Silicone rubber or the like can be used. The silicone rubber is polydimethylsiloxane and has a polymerization degree of 10
RTV silicone rubber based on liquid silicone rubber with a low degree of polymerization of 0 to 800 and degree of polymerization of 6000 to 1000
Millable silicone rubber based on 0 gel-like silicone raw rubber, etc. is conceivable. In all cases, anhydrous silica-based reinforcing filler such as Aerosil, increasing filler such as talc and mica, dispersion accelerator, etc. are added to raw rubber. It is supplied as a compounded rubber compound. The RTV silicone rubber is generally polydimethylsiloxane. As the millable silicone rubber, one having a methyl vinyl group introduced in an amount of 0.1 to 0.5 mol% is used in order to balance the crosslinkability and the physical properties. In addition, trifluoropropyl group-introduced FVMQ and phenyl group-introduced PVMQ
Etc., any of them can be used, and a mixture thereof can be used as well.

The surface-printed layer in the present invention is formed by mixing the silicone rubber with a vulcanizing agent, molding the surface-printed layer, and then vulcanizing it by a conventional method. As the vulcanizing agent contained in the compounded rubber, for example, an organic peroxide-based crosslinking agent can be used. Examples of the organic peroxide-based cross-linking agent include benzoyl peroxide, bis2,4-dichlorobenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, p-monochlorobenzoyl peroxide, and 2,5-dimethyl. -2
5-bis (tert-butylperoxy) hexane, tert-
Butyl cumyl peroxide and the like.

As the filler, inorganic fillers such as silicic acid anhydride, calcium carbonate, hard clay, barium sulfate, talc, mica, asbestos and graphite; organic fillers such as recycled rubber, powder rubber, asphalt, styrene resin and glue. Agents. The rubber hardness of the silicone-blended rubber is usually 20 to 80, preferably 40 to 40 in JIS A.
When the hardness is less than this, the deformation of the rubber becomes large and the pattern cannot be accurately transferred. On the other hand, when the hardness exceeds this, it becomes difficult for the rubber to receive the ink, which is not preferable.

The offset blanket of the present invention comprises a support layer and a surface printing layer having the above-mentioned structure. As the support layer, for example, a rubber material (rubber paste)
Examples include a laminate prepared by laminating a plurality of layers of base cloth impregnated with and at least one compressible layer provided as necessary. The base fabric is a woven fabric such as cotton, polyester and rayon. Examples of the rubber material to be impregnated include acrylonitrile-butadiene copolymer rubber and chloroprene rubber. These rubbers contain a certain amount of vulcanizing agent,
It contains a vulcanization accelerator and, if necessary, a thickener and the like. Then, the woven cloth is coated with the rubber agent by an appropriate application means such as a blade coating method. Then, the surface printing layer forming rubber paste made of the above-mentioned specific rubber material is applied to the surface of the support layer through the primer layer and dried, or a sheet-like material formed by a calendar or the like is laminated. The obtained laminate is heated and pressurized at a predetermined pressure and temperature to be vulcanized to obtain an offset blanket having a compressive layer in the support layer. The compressive layer is prepared by applying a rubber paste prepared by dissolving a water-soluble powder such as salt to at least one intermediate base cloth, drying and vulcanizing it, and then applying 6 to 10 to 10 to 100 ° C. hot water. It is formed by immersing for a time, eluting the water-soluble powder and drying.

Further, instead of such a laminated type support layer, a film or sheet such as polyethylene terephthalate (PET), polycarbonate (PC), polypropylene (PP), aluminum foil or stainless sheet is used as the support layer. May be. The obtained offset blanket is used by being adhered to the peripheral surface of the cylinder of the transfer cylinder either directly or through an undercoating material.

[0019]

[Examples] Compounding composition of the surface printing layer Example 1 Silicone rubber (a high-quality product manufactured by Shin-Etsu Chemical Co., Ltd. (Strength methyl vinyl silicone rubber compound) (hereinafter referred to as silicone rubber a), which contains 80% of a cross-linking agent C8A [2,5-dimethyl-2,5-bis (t-butylperoxy) hexane. What was done] was mixed at a predetermined ratio. Comparative Example 1 A commercially available silicone rubber (KE575U manufactured by Shin-Etsu Chemical Co., Ltd.) (hereinafter referred to as silicone rubber b) which is the same as that of Example 1 except that the low molecular weight siloxane and the non-functional silicone oil are not removed is used. , And mixed with a crosslinker as in Example 1. Comparative Example 2 Using a commercially available silicone rubber (KE9710U manufactured by Shin-Etsu Chemical Co., Ltd.) (hereinafter referred to as silicone rubber c), which was treated to remove only low molecular weight siloxane and not to remove nonfunctional silicone oil, It was mixed with the crosslinking agent in the same manner. Comparative Example 3 The same as Example 1 using a commercially available silicone rubber (KE556U manufactured by Shin-Etsu Chemical Co., Ltd.) (hereinafter referred to as silicone rubber d) in which only the nonfunctional silicone oil was removed without removing the low molecular weight siloxane. And mixed with the crosslinking agent.

Table 1 shows the mixing ratios of Example 1 and Comparative Examples 1 to 3.

[0021]

[Table 1]

Comparative Example 4 Further, acrylonitrile-butadiene copolymer rubber (N230 manufactured by Japan Synthetic Rubber Co., Ltd.) (hereinafter referred to as NBR) which has been conventionally used for a surface printing layer of an offset blanket was used, and the composition was as follows. A rubber composition for the surface printing layer was prepared. (Ingredient) (parts by weight) NBR 100 DOP (plasticizer) 10 Hard clay 40 Zinc oxide (# 1) 5 Stearic acid 1 Sulfur 1.5 Accelerator TT ^{* 1} 1.0 Accelerator DM ^{* 2} 1.5 * 1 Tetramethylene thiuram disulfide * 2 Dibenzothiazyl disulfide vulcanization conditions Primary vulcanization of each of the silicone rubbers of Example 1 and Comparative Examples 1 to 20 was performed at 170 ° C for 20 minutes, and secondary vulcanization was further performed.
It was carried out at 0 ° C. for different times. The NBR of Comparative Example 4 is 140
Vulcanization was performed at 30 ° C. for 30 minutes.

The above silicone rubber and NBR were laminated on a film of polyethylene terephthalate having a thickness of 350 μm so as to have a thickness of 750 μm, and then vulcanized to obtain an offset blanket having a total thickness of 1.0 mm. Since the surface of the mold was very smooth, the roughness was very smooth with RZ = 1.0 μm. Printing test The offset blanket obtained in each of the examples and comparative examples was mounted on a flatbed printing machine (Ector 600CL manufactured by Koyosha Co., Ltd.), and the offset blanket was placed on soda lime glass (thickness 1.1 mm) without ink. It was pressed and rotated three times. The soda lime glass was used after being ultrasonically cleaned in isopropyl alcohol for 30 minutes and dried.

The water repellency of the surface of the glass just washed and the glass of which the offset blanket was pressure-bonded and rotated three times was measured by an acrylic monomer (KAYARAD manufactured by Nippon Kayaku Co., Ltd.).
“MANDA”) was used for evaluation by the droplet method. That is, the contact angle of the droplet formed by the acrylic monomer on the surface of the surface printing layer was measured using a CA-A type machine manufactured by Kyowa Interface Science Co., Ltd. The results are shown in Table 2 along with the low molecular weight siloxane concentration and the non-functional silicone oil concentration.

[0025]

[Table 2]

From Table 2, in order to reduce the contamination on the glass surface and reduce the water repellency that repels the ink, the removal of the low molecular weight siloxane is not very effective, and the reaction in the silicone oil contained in the polymer is not effective. It can be seen that it is necessary to remove the non-functional non-functional silicone oil component. Further, it can be seen that it is preferable to reduce the respective concentrations of the low molecular weight siloxane and the non-functional silicone oil to 1500 ppm or less, judging from the contact angle of the ink monomer. Example 2 As a room temperature curing (RTV) silicone rubber, a dimethylsiloxane type RTV silicone rubber (manufactured by Shin-Etsu Chemical Co., Ltd.) from which low molecular weight siloxane and nonfunctional silicone oil were removed was used. 50 parts by weight of the main component of this dimethylsiloxane type RTV silicone rubber and a curing agent 5
0 parts by weight were mixed.

That is, the silicone rubber used is what is called an addition type two-component RTV silicone rubber,
Main agent (polysiloxane having vinyl group) and curing agent (H
A mixture of a polysiloxane having a —Si bond and a platinum catalyst). The reaction proceeds by the addition of the ≡Si group in the curing agent to the vinyl group of the polysiloxane, which is the main agent, by the action of the platinum catalyst. Example 3 In the same manner as in Example 2 except that a phenyl type RTV silicone rubber (manufactured by Shin-Etsu Chemical Co., Ltd.) from which low molecular weight siloxane and a nonfunctional silicone oil were removed was used instead of the dimethylsiloxane type RTV silicone rubber. 50 parts by weight of the main agent and 50 parts by weight of the curing agent were mixed. Comparative Example 5 Using a commercially available dimethyl siloxane type commercially available RTV silicone rubber, 100 parts by weight of the main agent (KE103 manufactured by Shin-Etsu Chemical Co., Ltd.) was used as a platinum catalyst (Cat-10 manufactured by Shin-Etsu Chemical Co., Ltd.).
Mixed with 5 parts by weight of 3). Comparative Example 6 Using a commercially available dimethyl siloxane type RTV silicone rubber having a reduced low molecular weight siloxane concentration, 50 parts by weight of a main agent (KE1204AL manufactured by Shin-Etsu Chemical Co., Ltd.) and 50 parts by weight of a curing agent (KE1204BL manufactured by Shin-Etsu Chemical Co., Ltd.) Mixed with. Comparative Example 7 Using a phenyl type commercially available RTV silicone rubber,
50 parts by weight of the main agent (KE109A manufactured by Shin-Etsu Chemical Co., Ltd.) was mixed with 50 parts by weight of a curing agent (KE109B manufactured by Shin-Etsu Chemical Co., Ltd.).

Vulcanization Conditions For Examples 2 and 3 and Comparative Examples 5 to 7 described above, a thickness of 0.8 mm was formed on the surface of a polyethylene terephthalate film (“Lumirror” manufactured by Toray Industries, Inc., thickness 200 μm). Coat the above silicone rubber and let it stand for 24 hours at room temperature to cure it without dust,
An offset blanket having a total thickness of 1.0 mm was produced.
The roughness of the surface was RZ = 0.8 μm, which was very smooth. Printing test Each of the offset blankets obtained in Examples 2 and 3 and Comparative Examples 5 to 7 was mounted on a flatbed printing machine in the same manner as in the printing test described above and washed soda lime glass (thickness 1.1 m).
m) Pressed and rotated 3 times without ink on top. Then, similarly to the above, water repellency was evaluated by a droplet method using an acrylic monomer. The results are shown in Table 3 together with the low molecular weight siloxane concentration and the non-functional silicone oil concentration.

[0029]

[Table 3]

From Table 3, it can be seen that by reducing both the low molecular weight siloxane concentration and the non-functional silicone oil concentration to 1500 ppm or less, the glass surface is less contaminated and the water repellency is reduced.

[0031]

As described above, according to the offset blanket for printing of the present invention, the low molecular weight siloxane and the non-functional silicone oil in the surface of the surface printing layer formed of silicone rubber have the respective concentrations of 1500 ppm.
Since it has been reduced to the following, especially in multicolor printing of fine patterns such as liquid crystal color filters, the water-repellent component is transferred from the surface printing layer to the surface of the printing material, and the ink is repelled on the surface of the printing material. It is also possible to prevent the water-repellent component from being transferred by the contact of the surface-printing layer with the printed pattern surface even after printing, and to form pinholes in the protective film coating the pattern surface. Can be prevented.

Therefore, the offset blanket for printing of the present invention is capable of almost completely transferring the ink transferred from the plate onto the glass plate without deteriorating the characteristics of the silicone rubber and performing multicolor printing of a fine pattern such as a liquid crystal color filter. In addition, it is possible to prevent pinholes and missing lines from being formed in the printed pattern. Therefore, it becomes possible to manufacture electronic components and liquid crystal color filters by a printing method with high throughput.

Claims (1)

[Claims] 1. An offset blanket for printing, comprising a surface printing layer made of silicone rubber laminated on a support layer, wherein the degree of polymerization on the surface of the surface printing layer is 20.
An offset blanket for printing, wherein the concentration of each of the following low molecular weight siloxane and non-functional silicone oil is 1500 ppm or less.